Expression control of electronic musical instrument

ABSTRACT

A light-sensitive variable resistor is connected in series between a tone filter circuit and an amplifier of an electronic musical instrument in order to give expression to musical performance by the instrument. In parallel with the lightsensitive variable resistor is connected a gate circuit which normally is nonconductive. Upon failure of a lamp adapted to regulate the electrical resistance offered by the light-sensitive variable resistor to the passage therethrough of the output signal from the tone filter circuit, the gate circuit becomes conductive to provide a bypass for the signal. An alarm lamp may be provided to visually indicate the lamp failure.

United States Patent 1191 Okamoto et al.

1 51 Oct. 22, 1974 [54] EXPRESSION CONTROL OF ELECTRONIC 3,671,955 6/1972 Malekzadeh 340/251 MUSICAL INSTRUMENT 3,672,253 6/1972 Hiyama 84/l.27

l Sh 0k t T t mu Ishii, Us] Mentors gl f gg g r g Primary Examiner-R1chard B. W lkinson I Assistant ExammerStanley J. W1tkowsk1 1 i W-" pp Gflkkl Sell" Kabushlk' Attorney, Agent, or Firm-Kcnncth S. Goldfnrb Kaisha, Hamamatsu-shi. Japan [21] APPL 300591 A light-sensitive variable resistor is connected in series between a tone filter circuit and an amplifier of an [52] US. Cl 84/l.27, 84/D1G. 19, 330/59, electronic musical instrument in order to give expres- 340/251 sion to musical performance by the instrument. In par- [51] Int. Cl. G10h 1/02 allel with the light-sensitive variable resistor is con- [58] Field of Search 84/ l .01, 1.09, 1.1, 1.18, nected a gate circuit which normally is nonconductive.

84/l.24, 1.25, 1.27, DIG. 19; 250/199, 217 Upon failure of a lamp adapted to regulate the electri- R, 552; 340/251; 330/59 cal resistance offered by the light-sensitive variable resistor to the passage therethrough of the output signal [56] References Cited from the tone filter circuit, the gate circuit becomes UN STATES PATENTS conductive to provide a bypass for the signal. An 2 836 766 5/1958 Halsted 250/217 R x alarm lamp may be Provided Visually indicate the 3,365,993 l/l968 Schwartz et al. 84/l.0l lamp fallure- 3,513,24 5/1970 Anderson et al. 84/l.l8 3,541,504 11/1970 Bush 340/251 x 10 m 5 D'awmg 1 l 6 AT E CIRCUIT 11 $15153 kW AMP PAIENIEDBBIZZIQM SIEEIIWE AMP GATE

FILTER CIRCUIT CIRCUIT CIRCUIT PArsmmwzz 3342.703

' SIEEI 2W 3 GATE CIRCUIT l 111 FILTER o-- I AMP 1 CIRCUIT F:

K 17 g 1o 26 12 13 FIGA 1 1 FILTER 1N CIRCUIT w] 5 AMP Q PAIENIED 021221914 FIGS FILTER CIRCUIT EXPRESSION CONTROL OF ELECTRONIC MUSICAL INSTRUMENT This invention relates generally to electronic musical instruments, and in particular to a novel and improved expression control of an electronic musical instrument such as, perhaps most importantly, an electronic organ,

Heretofore, to give greater expressiveness to musical performance by an electronic organ and like electronic musical instruments, a light-sensitive variable resistor such as cadmium sulphide has been usually connected in series between a tone filter or voicing" circuit and an amplifier of the electronic musical instrument. A shutter positioned between this light-sensitive variable resistor and an adjacently provided light source such as a lamp is movable by the expression pedal of the instrument to vary the intensity of light incident on the lightsensitive variable resistor from the light source and hence to correspondingly vary the electrical resistance offered thereby to the passage of the output signal from the tone filter circuit. The signal whose level has been thus regulated is then amplified and is translated by a loudspeaker into audible sound having a desired volume.

However, in this type of expression control, the lamp often goes off during performance, either upon termination of its predestined service life or due to the inevitable mechanical vibrations of the musical instrument.

- Upon failure of this lamp the electrical resistance of the light-sensitive variable resistor increases to such an extent that the level of the output signal from the expression control circuit becomes inordinately low. The loudspeaker of the musical instrument will then produce no audible sound, and musical performance must be discontinued pending replacement of the lamp.

In view of the noted inefficiencies of the prior art, it is an object of the present invention to provide a novel and improved expression control for an electronic musical instrument whereby musical performance can be continued uninterruptedly in the event of a failure of a light source positioned opposite a light-sensitive variable resistor adapted for expression control purposes.

Another object of the invention is to provide an expression control of simple and inexpensive configuration which can be easily incorporated in an electronic musical instrument such as an electronic organ without substantially increasing the manufacturing costs thereof.

A further object of the invention is to provide an expressed control in which a gate circuit is connected in parallel with the light-sensitive variable resistor which may be connected between a tone filter circuit and an amplifier of an electronic musical instrument, in such a manner that the gate circuit becomes conductive upon failure of the light source to provide a bypass for the output signal from the tone filter circuit.

A further object of the invention is to provide an expression control for an electronic musical instrument in which alarm means is provided to visually indicate a failure of the light source whenever this happens.

A further object of the invention is to provide an expression control for an electronic musical instrument in which at least one additional light source is provided in side-by-side relationship with the light source which is kept lit up during operation of the electronic musical instrument to irradiate the light-sensitive variable resistor, the additional light source becoming operative upon failure of the regular light source for uninterrupted musical performance.

Still a further object of the invention is to provide an expression control for an electronic musical instrument in which two or more light sources are positioned in side-by-side relationship opposite the light-sensitive variable resistor and are both lit up throughout operation of the electronic musical instrument, so that uninterrupted muscial performance is ensured despite failure of either of the light sources.

With these objects in view and the other objects, features and advantages of the present invention hereinafter made apparent, the invention will now be described more specifically with reference to the accompanying drawings, in which like reference characters designate like circuit elements throughout the several diagrams, and wherein:

FIGS. 1 to 5 inclusive are electrical schematic diagrams showing different preferred embodiments of the invention.

A first preferred embodiment of the invention will now be described with reference to FIG. I. An input terminal IN of a tone filter circuit 10 is connected to a suitable tone-generating source of the electronic musical instrument not shown in the drawing. The output of the tone filter circuit 10 is connected via a lightsensitive variable resistor 11 such for example as cadmium sulphide to an amplifier l2 and thence to a loudspeaker 13. v

Positioned opposite the light-sensitive variable resistor 11 is a lamp 14 which is connected via a resistance 15 to a power supply 16 capable of producing a direct current, the positive terminal of the power supply 16 being grounded as in the drawing. A shutter 17, perforated in the manner well known to those in the art, is provided between the light-sensitive variable resistor 11 and the lamp 14. Linked to the expression pedal, not shown, of the electronic musical instrument, the shutter 17 can be moved relative to the photoconductive element 11 and the lamp 14 by the performer in order to vary the intensity of light impinging on the former from the latter and hence to correspondingly vary the electrical resistance thereof in accordance with the prior art.

A gate circuit 18 is connected in parallel with the light-sensitive variable resistor 11, and the control terminal of this gate circuit 18 is connected to a point a of connection between the lamp 14 and the resistance 15.

The first preferred embodiment of the invention being configured substantially as hereinbefore described, the electrical signal from the aforesaid tonegenerating source is introduced through the input terminal IN into the tone filter circuit 10 for the voicing operation, in which the signal is suitably processed so as to have the tone of a desired musical instrument such for example as a violin. The output signal from the tone filter circuit 10 is impressed to the light-sensitive variable resistor 11.

If now the performer of the electronic musical instrument operates the expression pedal, the shutter 17 will move in a well known manner relative to the lightsensitive variable resistor 11 and the lamp 14 to vary the intensity of the rays of light traveling therethrough from the latter to the former. In accordance with the thus-modified intensity of the incident light, the lightsensitive'variable resistor 11 has its electrical resistance varied and correspondingly regulates the level of the signal impressed thereto from the tone filter circuit as aforesaid. This signal is then amplified by the amplifier 12 and is succeedingly translated into audible sound by the loudspeaker 13.

In the normal working condition of the lamp 14, the electrical potential at the point a will be approximately equal to that at the negative terminal of the power supply 16 if it is understood that the internal resistance of the lamp 14 is negligible compared to the resistance 15. Accordingly, the control terminal of the gate circuit 18 is at a negative potential, so that the gate circuit is held nonconductive during the normal working condition of the lamp 14. g

In the event of a failure of the lamp 14, the electrical resistance of the light-sensitive variable resistor 11 becomes substantially infinitely great, thereby preventing the passage therethrough of the output signal from the tone filter circuit 10 to the amplifier 12. However, the potential at the point a at this instant becomes. closer to that of the grounded positive terminal of the power supply 16, so that conduction takes place through the gate circuit 18. The output signal from the tone filter circuit 10 is now delivered to the amplifier 12 via the gate circuit 18, thereby bypassing the light sensitivevariable resistor 11, and the sound having a predetermined constant volume is produced by the loudspeaker 13.

If desired, the resistance may be replaced by a variable resistor, and a knob or the like for changing its resistance may be positioned within easy reach of the performer. It is possible in this manner to regulate the level of the signal from the tone filter circuit 10, so that expression control can be carried out almost uninterruptedly if the lamp 14 goes off during performance.

FIG. 2 illustrates another preferred embodiment of the invention, in which a field-effect transistor (hereinafter referred to simply as the FET) 19 is provided in lieu of the gate circuit 18 in the preceding embodiment. The FET 19 has its drain connected to the output of the tone filter circuit 10 via a resistance 20, its source to the input of the amplifier l2, and its gate to the point a of connection between the lamp 14 and the resistance 15 via a resistance 21. This point 'a is grounded via the resistance 15, and the other terminal of the lamp 14 is connected to the negative terminal of the power supply 16, the positive terminal of which is grounded.

The negative terminal of the power supply 16 is further connected to the emitter of a transistor 22 which in combination with a second lamp 23 constitutes an alarm section 24. The collector of the transistor 22 is FIG. 1 embodiment.

In event the lamp 14 goes off, the positive ground potential at the point a is impressed to the gate of the FET 19 to render the same conductive. The output signal from the tone filter circuit 10 is now permitted to travel through the resistance 20 and the drain and source of the FET 19 to the amplifier l2 and thence to the loudspeaker 13. Simultaneously, the potential at the point a is also introduced to the base of the transistor 22 via the resistance 25 to cause conduction therethrough, so that the second lamp 23 of the alarm section 24 is now lit up to indicate the failure of the first mentioned lamp 14.

Illustrated in FIG. 3 is a third preferred embodiment of the invention, which may be considered a modification of the FIG. 1 embodiment. The lamp 14 in this third embodiment is connected directly to both terminals of the power supply 16, the positive terminal of which is grounded, and a second light-sensitive variable resistor 26 is disposed opposite the lamp 14. This second light-sensitive variable resistor 16 is connected via a resistance 27 to a second power supply 28 capable of producing a direct current, the positive terminal of the second power supply 28 being also grounded. A point b of connection between the second light-sensitive variable resistor 26 and the resistance 27 is connected to the control terminal of the gate circuit 18.

Upon failure of the lamp 14 in this third embodiment of the invention, not only the first light-sensitive variable resistor 11 but the second light-sensitive variable resistor 26 has its resistance increased to such an extent that the positive potential developed at the point b is impressed to the control terminal of the gate circuit 18 to cause conduction therethrough as in the FIG. 1 embodiment.

FIG. 4 illustrates a further preferred embodiment of the invention, in which two lamps l4 and 29 are positioned in side-by-side relationship on the opposite side of the light-sensitive variable resistor 11 with respect to the shutter 17, so that the expression controlling operation can be continued without interruption if one of the lamps goes off. One, of the terminals of the lamp 14 is connected to the negative terminal of the power supply 16, the positive terminal of which is grounded, and the other terminal of the lamp 14 is grounded via the resistance 15. The point a of connection between the lamp l4 and the resistance 15 is connected to the base of a transistor 30 which performs a switching function in a manner hereinafter referred to.

The emitter of the transistor 30 is connected to the negative terminal of the power supply 16, and its collector is connected to one of the terminals of the lamp 29. Both terminals of this lamp 29 are connected respectively to both terminals of the lamp 23 of the alarm section 24. A point 0 of connection between one of the terminals of the lamp 23 and one of the terminals of the lamp 29 is grounded.

As may be apparent from FIG. 4, the gate circuit 18 connected in parallel with the light-sensitive variable resistor 11 in all the preceding embodiments of the invention shown in FIGS. 1 to 3 is absent in this embodiment. In the normal operative condition of the lamp 14, the electrical potential at the point a is equal to that obtained by dividing the voltage of the power supply 16 by the internal resistance of the lamp 14 and the resistance 15. Since the resistance 15 is sufficiently greater than the internal resistance of the lamp 14 as previously mentioned, the potential at the point a will be approximately equal to that at the negative terminal of the power supply 16, so that the transistor 30 is held nonconductive. Neither the lamp 29 nor the lamp 23 is now lit up.

When the lamp 14 goes off, the point a assumes a positive ground potential. This potential is introduced to the base of the transistor 30 to cause conduction therethrough, whereupon the other lamp 29 is lit up for the sustained expression controlling operation. The lamp 23 is also lit up to indicate the failure of the lamp 14. This lamp 23 may be disposed at a position readily observable by the performer, so that he can confirm prior to performance if the lamp 14 is in proper operable condition.

It will be easy for those in the art to devise a modification of this embodiment in l which three or more lamps are provided instead of the two lamps 14 and 29 shown in FIG. 4. Further, the means for lighting up the lamp 23 of the alarm section 24 is not limited to the example shown in this drawing but is open to many other modifications which may fall within the scope of this invention.

FIG. 5 illustrates still a further preferred embodiment of the invention, in which two lamps 14 and 31 positioned in side-by-side relationship on the opposite side of the light-sensitive variable resistor 11 with respect to the shutter 17 are both kept lit up throughout operation of the electronic musical instrument. If one of these lamps goes off, the other lamp will remain in operation to make possible to continue the expression controlling operation without interruption. One of the terminals of each of these lamps 14 and 31 is grounded via resistance 15 or 32, and the other terminal thereof is connected to the negative terminal of the power supply 16 the positive terminal of which is grounded. The parallel-connected lamps 14 and 31 are both kept lit up by the power supply 16 during performance.

The point a of connection between the lamp 14 and the resistance 15 is connected to the base of the transistor 22 via a diode 33, and a point 0' of connection between the other lamp 31 and the resistance 32 issimilarly connected to the base of the transistor 22 via a diode 34. This transistor 22 is associated within the lamp 23 to form the alarm section 24 as in the FIG. 2 embodiment.

When the lamps 14 and 31 are both in their normal working condition, the electrical potentials at the points a and d are equal to those obtained by dividing the voltage of the power supply 16 by the internal resistance of the lamp l4 and the resistance 15 and by the internal resistance of the lamp 31 and the resistance 32, respectively. Since it is assumed that the resistances 15 and 32 are respectively sufficiently greater than the internal resistances ofthe lamps 14 and 31, the potentials at the points a and d are approximately equal to that at the negative terminal of the power supply 16, so that the diodes 33 and 34 and therefore the transistor 22 are all nonconductive. The lamp 23 of the alarm section 24 is also unlit.

in event either of the lamps 14 and 31, for example, the lamp 14, goes off, the point a assumes a positive potential thereby forwardly biasing the diode 33 to cause conduction therethrough, with the result that the biasing voltage is impressed to the base of the transistor 22 to render the same conductive. The lamp 23 is thus lit up to indicate the fact that either of the lamps 14 and 31 (14 in this case) has failed. However, the other lamp (31 in this case) still remains in operation to regulate the electrical resistance of the light-sensitive variable resistor 11 through the shutter 17 and hence to control the level of the signal delivered by the tone filter circuit 10 in the usual manner.

It will be understood that there is practically very little probability of the lamps l4 and 31 going off altogether during the performance of the electronic musical instrument. However, if desired, three or more lamps may be provided instead of the two lamps 14 and 31 as previously mentioned in relation with the FlG. 4 embodiment.

While the present invention has been shown and described hereinbefore in terms of some preferred embodiments thereof, it will be understood that the invention itself is not intended to be restricted by the exact showing of the drawings and the description thereof but is considered to include a latitude of modification, substitution and change. It is, therefore, appropriate that the appended claims be construed broadly and in a manner consistent with the spirit and scope of the invention as herein disclosed.

We claim:

1. An expression control circuit for an electronic musical instrument comprising a light-sensitive variable resistor for regulating the level of an electrical signal passing therethrough, a light source positioned so as to be directed onto said light-sensitive variable resistor and kept lit up during operation of the electronic musical instrument, at least one other light source also positioned so as to be directed onto said light-sensitive variable resistor and kept unlit during normal operation of the first mentioned light source, means for varying the intensity oflight incident on said light-sensitive variable resistor from the first mentioned light source to correspondingly vary the resistance by said light-sensitive variable resistor to the passage therethrough of said electrical signal, said means being also capable of varying the intensity of light incident on said light-sensitive variable resistor from the second mentioned light source when the same is lit up, a detection means coupled to said first mentioned light source for detecting failure of said first mentioned light source and switching means for lighting up the second mentioned light source upon failure of the first mentioned light source.

2. An expression control circuit according to claim 1, in which said light-sensitive variable resistor is connected between a tone filter and amplifier means for amplifying the signal received from said tone filter of the electronic musical instrument, said tone filter means supplying said electrical signal to said lightsensitive variable resistor.

3. An expression control circuit according to claim 1, further comprising alarm means operably connected to said detection means for making an indication upon failure of the first mentioned light source.

4. An expression control circuit according to claim 3, in which said alarm means includes a failure indication lamp which is lit up by said switching means upon failure of the first mentioned light source.

5. An expression control circuit for an electronic musical instrument comprising a light-sensitive variable resistor for regulating the level of an electrical signal passing therethrough, a plurality of light sources positioned in alignment with said light-sensitive variable resistor and kept lit up during operation of the electronic musical instrument, and means for varying the intensity of light incident on said light-sensitive variable resistor from said light sources to correspondingly vary the resistance offered by said light sensitive variable resistor to the passage therethrough of said electrical signal, a detection means coupled to said light sources for detecting failure of at least one of said light sources said light-sensitive variable resistor being connected between tone filter means and amplifier means of the electronic musical instrument, said tone filter means supplying said electrical signal to said light-sensitive variable resistor, and alarm means operably connected to said detection means for making an indication upon failure of at least one of said light sources.

6. An expression control circuit according to claim 5, in which said alarm means includes a failure indication lamp which is lit up upon failure of at least one of said light sources.

7. An expression control circuit for an electronic musical instrument comprising a light-sensitive variable resistor connected between tone filter and amplifier means for amplifying the signal from said tone filter of an electronic musical instrument, said light-sensitive variable resistor being adapted to regulate the level of an electrical signal passing therethrough from said tone filter means to said amplifier means, a light source positioned so as to be directed onto said light-sensitive variable resistor, means for varying the intensity of light incident on said light-sensitive variable resistor from said light source to correspondingly vary the resistance offered by said light-sensitive variable resistor to the passage therethrough of said electrical signal, a'detection means coupled to said light source for detecting failure of said light source, and gate means connected in parallel with said light-sensitive variable resistor and connected to said detection means, said gate means being normally nonconductive and being made conductive upon failure of said light source to permit the passage therethrough of said electrical signal at a predetermined level.

8. An expression control circuit according to claim 7, in which said gate means includes a field-effect transistor.

9. An expression control circuit according to claim 7, in which the operation of said gate means is controlled by a second light-sensitive variable resistor positioned with respect to said light source so that said light source is directed onto said second light-sensitive variable resister.

10. An expression control circuit according to claim 7, including alarm means for making an indication upon failure of said light source, said alarm means including a failure indicating lamp which is lit up upon failure of the first-mentioned light source. 

1. An expression control circuit for an electronic musical instrument comprising a light-sensitive variable resistor for regulating the level of an electrical signal passing therethrough, a light source positioned so as to Be directed onto said light-sensitive variable resistor and kept lit up during operation of the electronic musical instrument, at least one other light source also positioned so as to be directed onto said light-sensitive variable resistor and kept unlit during normal operation of the first mentioned light source, means for varying the intensity of light incident on said light-sensitive variable resistor from the first mentioned light source to correspondingly vary the resistance by said light-sensitive variable resistor to the passage therethrough of said electrical signal, said means being also capable of varying the intensity of light incident on said light-sensitive variable resistor from the second mentioned light source when the same is lit up, a detection means coupled to said first mentioned light source for detecting failure of said first mentioned light source and switching means for lighting up the second mentioned light source upon failure of the first mentioned light source.
 2. An expression control circuit according to claim 1, in which said light-sensitive variable resistor is connected between a tone filter and amplifier means for amplifying the signal received from said tone filter of the electronic musical instrument, said tone filter means supplying said electrical signal to said light-sensitive variable resistor.
 3. An expression control circuit according to claim 1, further comprising alarm means operably connected to said detection means for making an indication upon failure of the first mentioned light source.
 4. An expression control circuit according to claim 3, in which said alarm means includes a failure indication lamp which is lit up by said switching means upon failure of the first mentioned light source.
 5. An expression control circuit for an electronic musical instrument comprising a light-sensitive variable resistor for regulating the level of an electrical signal passing therethrough, a plurality of light sources positioned in alignment with said light-sensitive variable resistor and kept lit up during operation of the electronic musical instrument, and means for varying the intensity of light incident on said light-sensitive variable resistor from said light sources to correspondingly vary the resistance offered by said light sensitive variable resistor to the passage therethrough of said electrical signal, a detection means coupled to said light sources for detecting failure of at least one of said light sources said light-sensitive variable resistor being connected between tone filter means and amplifier means of the electronic musical instrument, said tone filter means supplying said electrical signal to said light-sensitive variable resistor, and alarm means operably connected to said detection means for making an indication upon failure of at least one of said light sources.
 6. An expression control circuit according to claim 5, in which said alarm means includes a failure indication lamp which is lit up upon failure of at least one of said light sources.
 7. An expression control circuit for an electronic musical instrument comprising a light-sensitive variable resistor connected between tone filter and amplifier means for amplifying the signal from said tone filter of an electronic musical instrument, said light-sensitive variable resistor being adapted to regulate the level of an electrical signal passing therethrough from said tone filter means to said amplifier means, a light source positioned so as to be directed onto said light-sensitive variable resistor, means for varying the intensity of light incident on said light-sensitive variable resistor from said light source to correspondingly vary the resistance offered by said light-sensitive variable resistor to the passage therethrough of said electrical signal, a detection means coupled to said light source for detecting failure of said light source, and gate means connected in parallel with said light-sensitive variable resistor and connected to said detEction means, said gate means being normally nonconductive and being made conductive upon failure of said light source to permit the passage therethrough of said electrical signal at a predetermined level.
 8. An expression control circuit according to claim 7, in which said gate means includes a field-effect transistor.
 9. An expression control circuit according to claim 7, in which the operation of said gate means is controlled by a second light-sensitive variable resistor positioned with respect to said light source so that said light source is directed onto said second light-sensitive variable resistor.
 10. An expression control circuit according to claim 7, including alarm means for making an indication upon failure of said light source, said alarm means including a failure indicating lamp which is lit up upon failure of the first-mentioned light source. 